Field of the Invention
A well established sterilization method employed by both hospitals and manufacturers of sterile goods employs an alkylene oxide, primarily ethylene or propylene oxide, of adjusted humidity, temperature, and concentration in an inert gas in an enclosed chamber to disinfect or sterilize especially heat-sensitive medical goods including, for example, medical and surgical instruments which are placed in the sterilizing chamber in packs, which constitute compact bundles of plastic or textile material to protect the instruments. A positive determination of the complete effectiveness of an alkylene oxide sterilization procedure can be determined by the kill factor of spores placed within the sterilization chamber during the process and subsequently cultured to determine the existence of any living microorganisms. This long and inconvenient procedure is routinely replaced by the placing of telltale indicators in the sterilization zone, which indicators by reaction with, for example, ethylene oxide indicate the presence of ethylene oxide, and, if properly buffered either physically or chemically, the presence of ethylene oxide for a sufficient period to ensure completed sterilization conditions.
Ethylene oxide while an efficient low temperature sterilant is an irritant that must be purged from the packs containing the articles being sterilized and from the articles themselves and this is routinely accomplished by an aeration procedure in which the sterilized goods are aerated in a chamber for a sufficient period to remove substantially all traces of the sterilant gas. The majority of sterilization indicators having reacted with the ethylene oxide to change color or to become colored are ineffective to monitor the subsequent aeration of the sterilized goods. Indicators which monitor the purging of ethylene oxide from medical goods in a sterilization method are disclosed in U.S. Pat. Nos. 3,738,811 and 3,992,154. The former patent discloses a method of frequent rupturing of an ampule and consequently permits only an approximation of the aerating cycle. The latter discloses a compound, 4(p-nitrobenzyl) pyridine which when suitably modified by other additives effects a color change by direct reaction with the ethylene oxide sterilant and then an additional color change by reaction of the resulting compound with air. A color changing indicator composition which relies upon changing the color of pH indicators for detecting the completion of sterilization by ethylene oxide but which is limited to monitoring solely the sterilization step and does not monitor the aeration procedure is disclosed in U.S. Pat. No. 4,015,937.
It is a primary object of this invention to provide a method and means for monitoring the alkylene-oxide sterilization and the subsequent aeration of medical goods, which means in part react first with the alkylene oxide to measure the sterilization process, and subsequently measure the aeration process, and in additional part include an indicator responsive to the result of aforesaid reactions which can be an altered potential or an alteration of the pH of the process to reflect, respectively, the completion of sterilization and aeration conditions.
It is a further object of the invention to provide a method of and means for monitoring the ethylene oxide sterilization of especially heat-sensitive medical goods and the subsequent desorption by aeration of the goods which method and means employ a strong acid cation exchange resin that will adsorb and react with the ethylene oxide and that subsequently will desorb the ethylene oxide (the aeration step) and an indicator means reflecting the result of said adsorption and subsequent desorption and so, by indicatorcolor change marking respectively the completion of sterilization and of aeration of the said goods.